Self-emptying punching tool

ABSTRACT

A self-discharging punching tool for use in the leather and textile industry is disclosed. The tool comprises a body portion with an endless cutting knife, the cutting knife being conically tapered relative to the perpendicular and being made from prehardened, finish-ground strip steel. The application also discloses a method for producing the selfdischarging punching tool according to which the hardened and preground strip steel is mechanically drawn or stretched for the production of inwardly and outwardly pointing curvatures, the stretching or drawing being effected at the cutting edge side for the production of inwardly pointing curvatures while the stretching or drawing takes place at the rear or back side for the production of outwardly pointing curvatures.

United States Patent 1191 Fauth Mar. 25, 1975 [54] SELF-EMPTYING PUNCHING TOOL 3,381,563 5/1968 Bishop 83/673 X l 1 G [75] Inventor Emil Fauth, Sandhausen ermany Pnmary ExaminerAndrew R Juhasz [73] Assignee: Firma Emil Fauth, Sandhausen near A i t t Ex mi r-W, D. Bray Heidelberg, G y Attorney, Agent, or Firm-Toren, McGeady and 22 Filed: Aug. 21, 1972 Slang" [21] App]. No.: 282,324 [57] ABSTRACT A self-discharging punching tool for use in the leather Foreign pp ri ri y Data and textile industry is disclosed. The tool comprises a Aug. 24. 1971 Germany....L 2142234 body portion with an endless cutting knife, the cutting 1 knife being conically tapered relative to the perpen- [52] US. Cl 76/107 C, 83/652, 83/686 dicular and being made from prehardened, finish- [51] Int. Cl C22b 3/02 ground strip steel. [58] Field of Search 83/698, 686, 673, 6 The application also discloses a method for producing 83/6521 6531 6541 6551 6561 6571 684; the self-discharging punching tool according to which 76/107 C the hardened and preground strip steel is mechanically drawn or stretched for the production of inwardly and [56] 7 References cued outwardly pointing curvatures, the stretching or UNITED STATES PATENTS drawing being effected at the cutting edge side for the 954,559 4/1910 Zimmerman 83/652 Production of inwardly Pointing curvatures While the 1,129,079 2/1915 Donaldson 83/652 stretching or drawing takes place at the rear or back 2,178,473 10/1939 Exley 83/686 X side for the production of outwardly pointing 2,2l 1,2 l 3 C X curvatures 3,152,492 10/1964 Whitecotton 76/107 C $205,732 9/1965 Hutcheon et a]. 76/109 c 5 s, 2 ra mg: lgures PATENIEI] MAR 2 5 I975 1 SELF-EMPTYING PUNCHING TOOL FIELD OF INVENTION The invention is directed to self-emptying or selfdischarging punching or cutting tools, particularly useful for use in the shoe industry for clicking shoe parts and the like. The invention is also directed to a method for manufacturing the novel punching tool.

BACKGROUND INFORMATION In the manufacture of shoes, the soles, the counters, the uppers and other shoe parts are clicked or punched from the blanks by means of punching or cutting tools (hereinafter referred to as punching tools). The general custom is to use for this purpose forged punching forms or patterns which, on the average have a weight of about 1.5 kg. Generally, about 600 punchings or clickings per hour can be carried out with such prior art punching forms.

It has also been suggested to manufacture punching forms from unhardened strip steel, thereby avoiding the forging step.

In both instances, to wit, whether forged punching forms or punching forms made from unhardened strip steel are used, the form must first be subjected to an annealing treatment for stress relief purposes, whereafter the form is hardened and tempered. Finally, the back or rear portion of the form has to be surface ground and the cutting edge has to be ground at the inner side relative to the circumferential surface of the form.

More recently, hardened and. ground knife edge strips have been proposed which in this condition are bent into punching forms of the desired pattern. However, it has not previously been possible to construct such punching forms so as to be self-discharging or selfemptying.

SUMMARY OF THE INVENTION It is a primary purpose of the present invention to overcome the drawbacks and disadvantages of prior art punching forms.

It is also an object of the invention to provide a punching form, particularly useful in the shoe industry, by means of which clicking of shoe parts can be accomplished in a superior manner.

Another object of the invention is to propose a method for manufacturing the punching forms of the invention which is simple to carry out with a minimum of equipment and expenditure.

Generally, it is an object of this invention to improve on the art of punching tools or forms as presently practised.

The invention is based on the realization that thermal treatment and grinding treatment which hitherto had to be performed on the punching form, can be successfully avoided by using hardened and ground strip steel having a cutting edge and to process suchstrip steel into a self-discharging form of the desired pattern.

Contrary to the prevailing prejudice, it has been ascertained that strip steel having a cutting edge which has been prehardened can be successfully cold-drawn or stretched in mechanical manner in the region of its back or cutting portions. It has thus been established that, after such strip steel has been bent into the desired punching pattern or shape, the tapering or slanting of the strip steel'which is necessary for self-emptying or discharge, can successfully be accomplished by correin cold condition.

Accordingly, the invention provides a selfdischarging punching tool for the leather and textile industry, particularly for the shoe industry which is characterized in that it has a cutting knife bent into an endless shape of the desired pattern, said cutting knife being conically tapered and being made from a prehardened pre-finish-ground strip steel. In a preferred embodiment, the tapering extends in an upward direction.

Particularly in respect of heavy tools, it is recommended that the cutting edge of the knife or punching tool is hollow-edged ground while the inclination or tapering of the knife amounts to about 4.5 relative to the perpendicular.

According to the inventive method for producing the novel punching tool, hardened and finish-ground strip steel having a knife edge and while being bent into the desired punching tool pattern is drawn or stretched in mechanical manner and in cold condition to form the desired pattern. Thus, when inwardly pointing curved portions are to be formed, the drawing or stretching is effected at the side of the cutting edge while for the formation of outwardly pointing curvatures the drawing or stretching is effected at the side of the back. A circumferential reinforcement in the nature of a frame member or the like may be connected to the outer side of the back or rear edge or the rear side, for example, by means of welding.

The self-discharging punching forms of this invention are significantly lighter in weight than prior art forms. Further, they are much simpler to produce since, as compared to the prior art forms made from forged steel or the like, the working steps of forging, surface grinding, filing, grinding of the knife edge, sharpening, hardening as well as tempering and polishing are eliminated.

An additional advantage resides in the fact that the inventive punching form is lighter in weight than the prior art constructions. Thus, the new forms can successfully be manufactured at a weight of about 1.0 kg as compared to forged steel forms which have a weight of 1.5 kg. Accordingly, .the new forms are significantly lighter, to wit, by an amount of about 0.5 kg. This means that if about 600 clickings or punchings are carried out per hour, the savings in weight per hour are about 300 kg. The inventive punching tools or knives may be produced in any desired shape, pattern and height, with or without reinforcing frame or the like strengthening means. The novel tools may be used in all branches of the textile and leather industry. If the knives are produced with hollow-edged cutting edges, an optimum degree of precision is obtained if multiple punchings of extremely thick layers, for example of FIG. 2 is a cross-sectional view through the tool of FIG. 1 along line A B, showing the outer tapering or inclination of the wall-forming portion of the tool.

Referring now to the drawings, the tool comprises a body portion of knife wall 1 which is made from strip steel which has previously been hardened and which has been finish-ground to form the knife edge 4. It will be noted that the knife wall 1 tapers or is inclined, the tapering or inclination being about 4.5 in an upward and outward direction. The knife wall 1 is reinforced by a frame member 2. The frame member 2 is rigidly connected with the knife member 1 by means of welding as indicated by reference numeral 3. The cutting edge 4 is thus endless and forms the desired pattern to be cut.

The inwardly curved portions of the cutting edge 4 are formed by stretching or drawing the strip steel at the cutting edge side while the outwardly directed curved portions are formed by drawing or stretching on the side of the back or rear. The mechanical working for forming the curvatures is accomplished while the steel is in cold condition.

The stretching or drawing of the strip steel is best effected in a device which has a hammer-like tool. The peen of the hammer extends transversely to the longitudinal direction of the steel strip. The hammer is struck .or pressed against the anvil of the device with the steel strip interposed. In this manner the thickness of the steel strip is locally reduced and the strip is thus stretched or drawn. If the hammer action is sufficiently strong, notches or indentations are formed in the surface of the steel. The greater the number of notches, the larger is the stretching of the strip. However, the notches or hammer impact areas are not formed over the entire width of the strip but are applied selectively to obtain the desired shaping result. When concave curvatures are intended, the notches are formed near the cutting edge while, by contrast, the notches or hammer impact areas are adjacent the back or rear edge of the form if convex curving is desired. If, for example, the rear or back of a rectangular form is stretched or drawn in the indicated manner by hammer action in the vicinity of the corners of the rectangle, then a conical punching tool or form is obtained which is wider at its rear or back than at the cutting edge.

EXAMPLE ously described. The stretching or drawing was effected mechanically and without heating. In order to form inwardly directed curvatures, the working, to wit the stretching or drawing, was done near the cutting edge side while outer curves were formed by working the shape adjacent the rear edge. It will be appreciated that forms or tools of any suitable shape and height can be thus produced. The hardness of the cutting edge of the punching tool produced in this manner amounted to 52 RC which corresponds to the hardness of forged knives. The inventive tools fulfill all the requirements which previously were met by forged punching tools only.

What is claimed is:

1. In a self-emptying punching tool for clicking shoe parts or cutting textile fabrics, including a body portion consisting of an elongated strip formed in an endless configuration extending longitudinally completely about an area enclosed by said strip, said strip including an inner wall facing toward said enclosed area, and an endless cutting edge extending longitudinally along said strip on one side of said inner wall, the improvement wherein said strip consists essentially of a single continuous strip of prehardened, finish-ground steel having two. ends joined together to form said endless configuration with said inner wall tapering to extend from said cutting edge outwardly away from said enclosed area with the area enclosed by said strip progressively increasing in size from the side of said inner wall at which said cutting edge is located to the side of said inner wall opposite said cutting edge, said strip being essentially composed of cold-formed material stretched longitudinally in a progressively increasing manner commencing from said knife edge, said knife edge consisting essentially of unstretched material which has been retained in its original circumferential length.

2. A tool according to claim 1 wherein said inner wall is formed with a taper which extends at an angle of 45 relative to a line extending perpendicularly to said enclosed area.

3. A method for producing a self-emptying punching tool comprising the steps of forming a prehardened and finish-ground elongated strip of steel having a knife edge on one side thereof into a continuous endless configuration which completely encloses an area about which said formed strip is shaped to circumferentially extend, and mechanically cold forming said endless strip to effect longitudinal stretching of said strip in a progressively increasing manner commencing from said knife edge while maintaining said knife edge in its original circumferential length, said cold-forming being effected while said strip is in said prehardened and finish-ground condition to form said strip into a configuration with the inner wall of said endless strip tapering from said knife edge outwardly relative to said enclosed area such that said enclosed area increases progressively from the side of said inner wall at which said knife edge is formed to the side of said inner wall opposite said knife edge.

4. A method according to claim 3 wherein said tapered wall extends at an angle of about 4.5 relative to a line extending perpendicularly to said enclosed area.

5. A method according to claim 3 wherein said end less configuration includes inwardly and outwardly pointing curvatures, said inwardly pointing curvatures being formed by mechanically stretching said steel strip at the side of said knife edge while said outwardly pointing curvatures are formed on the back side of said strip steel, said mechanical stretching being effected while said strip is in the cold condition. 

1. In a self-emptying punching tool for clicking shoe parts or cutting textile fabrics, including a body portion consisting of an elongated strip formed in an endless configuration extending longitudinally completely about an area enclosed by said strip, said strip including an inner wall facing toward said enclosed area, and an endless cutting edge extending longitudinally along said strip on one side of said inner wall, the improvemeNt wherein said strip consists essentially of a single continuous strip of prehardened, finish-ground steel having two ends joined together to form said endless configuration with said inner wall tapering to extend from said cutting edge outwardly away from said enclosed area with the area enclosed by said strip progressively increasing in size from the side of said inner wall at which said cutting edge is located to the side of said inner wall opposite said cutting edge, said strip being essentially composed of cold-formed material stretched longitudinally in a progressively increasing manner commencing from said knife edge, said knife edge consisting essentially of unstretched material which has been retained in its original circumferential length.
 2. A tool according to claim 1 wherein said inner wall is formed with a taper which extends at an angle of 4.5* relative to a line extending perpendicularly to said enclosed area.
 3. A method for producing a self-emptying punching tool comprising the steps of forming a prehardened and finish-ground elongated strip of steel having a knife edge on one side thereof into a continuous endless configuration which completely encloses an area about which said formed strip is shaped to circumferentially extend, and mechanically cold forming said endless strip to effect longitudinal stretching of said strip in a progressively increasing manner commencing from said knife edge while maintaining said knife edge in its original circumferential length, said cold-forming being effected while said strip is in said prehardened and finish-ground condition to form said strip into a configuration with the inner wall of said endless strip tapering from said knife edge outwardly relative to said enclosed area such that said enclosed area increases progressively from the side of said inner wall at which said knife edge is formed to the side of said inner wall opposite said knife edge.
 4. A method according to claim 3 wherein said tapered wall extends at an angle of about 4.5* relative to a line extending perpendicularly to said enclosed area.
 5. A method according to claim 3 wherein said endless configuration includes inwardly and outwardly pointing curvatures, said inwardly pointing curvatures being formed by mechanically stretching said steel strip at the side of said knife edge while said outwardly pointing curvatures are formed on the back side of said strip steel, said mechanical stretching being effected while said strip is in the cold condition. 